US20140092838A1 - Determining maximum power reduction (mpr) for multi-cluster wireless transmissions - Google Patents

Abstract

A method of wireless communication includes determining spectral positions of intermodulation distortion products for a multi-cluster transmission. The method also includes mapping the spectral positions to corresponding spectral regions. The method further includes determining a maximum power reduction value of the multi-cluster transmission based on the corresponding spectral regions.

Description

CROSS-REFERENCE TO RELATED APPLICATION
• This application claims the benefit under 35 U.S.C. §119(e) to U.S. Provisional Patent Application No. 61/708,995 entitled “DETERMINING MAXIMUM POWER REDUCTION (MPR) FOR MULTI-CLUSTER WIRELESS TRANSMISSIONS,” filed on Oct. 2, 2012, the disclosure of which is expressly incorporated by reference herein in its entirety.
BACKGROUND
• 1. Field
• Aspects of the present disclosure relate generally to wireless communication systems, and more particularly to power control in wireless systems, such as long term evolution (LTE) systems.
• 2. Background
• Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, and broadcasts. Typical wireless communication systems may employ multiple-access technologies capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth, transmit power). Examples of such multiple-access technologies include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, single-carrier frequency divisional multiple access (SC-FDMA) systems, and time division synchronous code division multiple access (TD-SCDMA) systems.
• These multiple access technologies have been adopted in various telecommunication standards to provide a common protocol that enables different wireless devices to communicate on a municipal, national, regional, and even global level. An example of an emerging telecommunication standard is Long Term Evolution (LTE). LTE is a set of enhancements to the Universal Mobile Telecommunications System (UMTS) mobile standard promulgated by Third Generation Partnership Project (3GPP). It is designed to better support mobile broadband Internet access by improving spectral efficiency, lower costs, improve services, make use of new spectrum, and better integrate with other open standards using OFDMA on the downlink (DL), SC-FDMA on the uplink (UL), and multiple-input multiple-output (MIMO) antenna technology. However, as the demand for mobile broadband access continues to increase, there exists a need for further improvements in LTE technology. Preferably, these improvements should be applicable to other multi-access technologies and the telecommunication standards that employ these technologies.
• This has outlined, rather broadly, the features and technical advantages of the present disclosure in order that the detailed description that follows may be better understood. Additional features and advantages of the disclosure will be described below. It should be appreciated by those skilled in the art that this disclosure may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present disclosure. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the teachings of the disclosure as set forth in the appended claims. The novel features, which are believed to be characteristic of the disclosure, both as to its organization and method of operation, together with further objects and advantages, will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present disclosure.
SUMMARY
• In one aspect of the present disclosure, a method of wireless communication is presented. The method includes determining spectral positions of intermodulation distortion products for a multi-cluster transmission. The method also includes mapping the spectral positions to corresponding spectral regions. The method further includes determining a maximum power reduction value of the multi-cluster transmission based on the corresponding spectral regions.
• Another aspect of the present disclosure is directed to an apparatus including means for determining spectral positions of intermodulation distortion products for a multi-cluster transmission. The apparatus also includes means for mapping the spectral positions to corresponding spectral regions. The apparatus further includes means for determining a maximum power reduction value of the multi-cluster transmission based on the corresponding spectral regions.
• In yet another aspect of the present disclosure, a computer program product for wireless communications in a wireless network having a non-transitory computer-readable medium is disclosed. The computer readable medium has non-transitory program code recorded thereon which, when executed by the processor(s), causes the processor(s) to perform operations of determining spectral positions of intermodulation distortion products for a multi-cluster transmission. The program code also causes the processor(s) to map the spectral positions to corresponding spectral regions. The program code further causes the processor(s) to determine a maximum power reduction value of the multi-cluster transmission based on the corresponding spectral regions.
• Another aspect of the present disclosure is directed to a wireless communication apparatus having a memory and at least one processor coupled to the memory. The processor(s) is configured to determine spectral positions of intermodulation distortion products for a multi-cluster transmission. The processor(s) is also configured to map the spectral positions to corresponding spectral regions. The processor(s) is further configured to determine a maximum power reduction value of the multi-cluster transmission based on the corresponding spectral regions.
• Additional features and advantages of the disclosure will be described below. It should be appreciated by those skilled in the art that this disclosure may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present disclosure. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the teachings of the disclosure as set forth in the appended claims. The novel features, which are believed to be characteristic of the disclosure, both as to its organization and method of operation, together with further objects and advantages, will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present disclosure.
BRIEF DESCRIPTION OF THE DRAWINGS
• The features, nature, and advantages of the present disclosure will become more apparent from the detailed description set forth below when taken in conjunction with the drawings in which like reference characters identify correspondingly throughout.
• FIG. 1 is a diagram illustrating an example of a network architecture.
• FIG. 2 is a diagram illustrating an example of an access network.
• FIG. 3 is a diagram illustrating an example of a downlink frame structure in LTE.
• FIG. 4 is a diagram illustrating an example of an uplink frame structure in LTE.
• FIG. 5 is a diagram illustrating an example of a radio protocol architecture for the user and control plane.
• FIG. 6 is a diagram illustrating an example of an evolved Node B and user equipment in an access network.
• FIG. 7 is a diagram illustrating a multi-cluster transmission spectrum and its associated intermodulation distortion products.
• FIG. 8 is a diagram illustrating a multi-cluster transmission spectrum and boundaries of its associated intermodulation distortion products.
• FIG. 9 is a diagram illustrating a region index mapping based on frequency offsets of intermodulation distortion products according to an aspect of the present disclosure.
• FIG. 10 is a table mapping region index combinations of intermodulation distortion products to a maximum power reduction value according to aspects of the present disclosure.
• FIG. 11 is a diagram illustrating an unbalanced multi-cluster transmission.
• FIG. 12 is a flow diagram illustrating a method of defining MPR depending on total number of resource blocks (RBs) for balanced and unbalanced clusters according to an aspect of the present disclosure.
• FIGS. 13 and 14 are flow diagrams illustrating methods for power control in wireless systems according to aspects of the present disclosure.
• FIG. 15 is a diagram illustrating an example of a hardware implementation for an apparatus employing a power control system according to one aspect of the disclosure.
DETAILED DESCRIPTION
• The detailed description set forth below, in connection with the appended drawings, is intended as a description of various configurations and is not intended to represent the only configurations in which the concepts described herein may be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of the various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. In some instances, well-known structures and components are shown in block diagram form in order to avoid obscuring such concepts.
• Aspects of the telecommunication systems are presented with reference to various apparatus and methods. These apparatus and methods are described in the following detailed description and illustrated in the accompanying drawings by various blocks, modules, components, circuits, steps, processes, algorithms, etc. (collectively referred to as “elements”). These elements may be implemented using electronic hardware, computer software, or any combination thereof. Whether such elements are implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system.
• By way of example, an element, or any portion of an element, or any combination of elements may be implemented with a “processing system” that includes one or more processors. Examples of processors include microprocessors, microcontrollers, digital signal processors (DSPs), field programmable gate arrays (FPGAs), programmable logic devices (PLDs), state machines, gated logic, discrete hardware circuits, and other suitable hardware configured to perform the various functionality described throughout this disclosure. One or more processors in the processing system may execute software. Software shall be construed broadly to mean instructions, instruction sets, code, code segments, program code, programs, subprograms, software modules, applications, software applications, software packages, routines, subroutines, objects, executables, threads of execution, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise.
• Accordingly, in one or more exemplary embodiments, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or encoded as one or more instructions or code on a computer-readable medium. Computer-readable media includes computer storage media. Storage media may be any available media that can be accessed by a computer. By way of example, and not limitation, such computer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer. Disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and Blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.
• FIG. 1 is a diagram illustrating anLTE network architecture100. TheLTE network architecture100 may be referred to as an Evolved Packet System (EPS)100. TheEPS100 may include one or more user equipment (UE)102, an Evolved UMTS Terrestrial Radio Access Network (E-UTRAN)104, an Evolved Packet Core (EPC)110, a Home Subscriber Server (HSS)120, and an Operator's IP Services122. The EPS can interconnect with other access networks, but for simplicity those entities/interfaces are not shown. As shown, the EPS provides packet-switched services, however, as those skilled in the art will readily appreciate, the various concepts presented throughout this disclosure may be extended to networks providing circuit-switched services.
• The E-UTRAN includes the evolved Node B (eNodeB)106 andother eNodeBs108. TheeNodeB106 provides user and control plane protocol terminations toward theUE102. TheeNodeB106 may be connected to theother eNodeBs108 via a backhaul (e.g., an X2 interface). TheeNodeB106 may also be referred to as a base station, a base transceiver station, a radio base station, a radio transceiver, a transceiver function, a basic service set (BSS), an extended service set (ESS), or some other suitable terminology. TheeNodeB106 provides an access point to theEPC110 for aUE102. Examples ofUEs102 include a cellular phone, a smart phone, a session initiation protocol (SIP) phone, a laptop, a personal digital assistant (PDA), a satellite radio, a global positioning system, a multimedia device, a video device, a digital audio player (e.g., MP3 player), a camera, a game console, or any other similar functioning device. TheUE102 may also be referred to by those skilled in the art as a mobile station, a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless device, a wireless communications device, a remote device, a mobile subscriber station, an access terminal, a mobile terminal, a wireless terminal, a remote terminal, a handset, a user agent, a mobile client, a client, or some other suitable terminology.
• TheeNodeB106 is connected to theEPC110 via, e.g., an S1 interface. TheEPC110 includes a Mobility Management Entity (MME)112,other MMEs114, aServing Gateway116, and a Packet Data Network (PDN)Gateway118. TheMME112 is the control node that processes the signaling between theUE102 and theEPC110. Generally, theMME112 provides bearer and connection management. All user IP packets are transferred through theServing Gateway116, which itself is connected to thePDN Gateway118. ThePDN Gateway118 provides UE IP address allocation as well as other functions. ThePDN Gateway118 is connected to the Operator's IP Services122. The Operator'sIP Services122 may include the Internet, the Intranet, an IP Multimedia Subsystem (IMS), and a PS Streaming Service (PSS).
• FIG. 2 is a diagram illustrating an example of anaccess network200 in an LTE network architecture. In this example, theaccess network200 is divided into a number of cellular regions (cells)202. One or more lowerpower class eNodeBs208 may havecellular regions210 that overlap with one or more of thecells202. The lowerpower class eNodeB208 may be a remote radio head (RRH), a femto cell (e.g., home eNodeB (HeNodeB)), pico cell, or micro cell. Themacro eNodeBs204 are each assigned to arespective cell202 and are configured to provide an access point to theEPC110 for all theUEs206 in thecells202. There is no centralized controller in this example of anaccess network200, but a centralized controller may be used in alternative configurations. TheeNodeBs204 are responsible for all radio related functions including radio bearer control, admission control, mobility control, scheduling, security, and connectivity to theserving gateway116.
• The modulation and multiple access scheme employed by theaccess network200 may vary depending on the particular telecommunications standard being deployed. In LTE applications, OFDM is used on the downlink and SC-FDMA is used on the uplink to support both frequency division duplexing (FDD) and time division duplexing (TDD). As those skilled in the art will readily appreciate from the detailed description to follow, the various concepts presented herein are well suited for LTE applications. However, these concepts may be readily extended to other telecommunication standards employing other modulation and multiple access techniques. By way of example, these concepts may be extended to Evolution-Data Optimized (EV-DO) or Ultra Mobile Broadband (UMB). EV-DO and UMB are air interface standards promulgated by the 3rd Generation Partnership Project 2 (3GPP2) as part of the CDMA2000 family of standards and employs CDMA to provide broadband Internet access to mobile stations. These concepts may also be extended to Universal Terrestrial Radio Access (UTRA) employing Wideband-CDMA (W-CDMA) and other variants of CDMA, such as TD-SCDMA; Global System for Mobile Communications (GSM) employing TDMA; and Evolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, and Flash-OFDM employing OFDMA. UTRA, E-UTRA, UMTS, LTE and GSM are described in documents from the 3GPP organization. CDMA2000 and UMB are described in documents from the 3GPP2 organization. The actual wireless communication standard and the multiple access technology employed will depend on the specific application and the overall design constraints imposed on the system.
• TheeNodeBs204 may have multiple antennas supporting MIMO technology. The use of MIMO technology enables theeNodeBs204 to exploit the spatial domain to support spatial multiplexing, beamforming, and transmit diversity. Spatial multiplexing may be used to transmit different streams of data simultaneously on the same frequency. The data steams may be transmitted to asingle UE206 to increase the data rate or tomultiple UEs206 to increase the overall system capacity. This is achieved by spatially precoding each data stream (i.e., applying a scaling of an amplitude and a phase) and then transmitting each spatially precoded stream through multiple transmit antennas on the downlink. The spatially precoded data streams arrive at the UE(s)206 with different spatial signatures, which enables each of the UE(s)206 to recover the one or more data streams destined for thatUE206. On the uplink, eachUE206 transmits a spatially precoded data stream, which enables theeNodeB204 to identify the source of each spatially precoded data stream.
• Spatial multiplexing is generally used when channel conditions are good. When channel conditions are less favorable, beamforming may be used to focus the transmission energy in one or more directions. This may be achieved by spatially precoding the data for transmission through multiple antennas. To achieve good coverage at the edges of the cell, a single stream beamforming transmission may be used in combination with transmit diversity.
• In the detailed description that follows, various aspects of an access network will be described with reference to a MIMO system supporting OFDM on the downlink. OFDM is a spread-spectrum technique that modulates data over a number of subcarriers within an OFDM symbol. The subcarriers are spaced apart at precise frequencies. The spacing provides “orthogonality” that enables a receiver to recover the data from the subcarriers. In the time domain, a guard interval (e.g., cyclic prefix) may be added to each OFDM symbol to combat inter-OFDM-symbol interference. The uplink may use SC-FDMA in the form of a DFT-spread OFDM signal to compensate for high peak-to-average power ratio (PAPR).
• FIG. 3 is a diagram300 illustrating an example of a downlink frame structure in LTE. A frame (10 ms) may be divided into 10 equally sized sub-frames. Each sub-frame may include two consecutive time slots. A resource grid may be used to represent two time slots, each time slot including a resource block. The resource grid is divided into multiple resource elements. In LTE, a resource block contains 12 consecutive subcarriers in the frequency domain and, for a normal cyclic prefix in each OFDM symbol, 7 consecutive OFDM symbols in the time domain, or 84 resource elements. For an extended cyclic prefix, a resource block contains 6 consecutive OFDM symbols in the time domain and has 72 resource elements. Some of the resource elements, as indicated asR302,304, include downlink reference signals (DL-RS). The DL-RS include Cell-specific RS (CRS) (also sometimes called common RS)302 and UE-specific RS (UE-RS)304. UE-RS304 are transmitted only on the resource blocks upon which the corresponding physical downlink shared channel (PDSCH) is mapped. The number of bits carried by each resource element depends on the modulation scheme. Thus, the more resource blocks that a UE receives and the higher the modulation scheme, the higher the data rate for the UE.
• FIG. 4 is a diagram400 illustrating an example of an uplink frame structure in LTE. The available resource blocks for the uplink may be partitioned into a data section and a control section. The control section may be formed at the two edges of the system bandwidth and may have a configurable size. The resource blocks in the control section may be assigned to UEs for transmission of control information. The data section may include all resource blocks not included in the control section. The uplink frame structure results in the data section including contiguous subcarriers, which may allow a single UE to be assigned all of the contiguous subcarriers in the data section.
• A UE may be assigned resource blocks410a,410bin the control section to transmit control information to an eNodeB. The UE may also be assigned resource blocks420a,420bin the data section to transmit data to the eNodeB. The UE may transmit control information in a physical uplink control channel (PUCCH) on the assigned resource blocks in the control section. The UE may transmit only data or both data and control information in a physical uplink shared channel (PUSCH) on the assigned resource blocks in the data section. An uplink transmission may span both slots of a subframe and may hop across frequency.
• A set of resource blocks may be used to perform initial system access and achieve uplink synchronization in a physical random access channel (PRACH)430. ThePRACH430 carries a random sequence and cannot carry any uplink data/signaling. Each random access preamble occupies a bandwidth corresponding to six consecutive resource blocks. The starting frequency is specified by the network. That is, the transmission of the random access preamble is restricted to certain time and frequency resources. There is no frequency hopping for the PRACH. The PRACH attempt is carried in a single subframe (1 ms) or in a sequence of few contiguous subframes and a UE can make only a single PRACH attempt per frame (10 ms).
• FIG. 5 is a diagram500 illustrating an example of a radio protocol architecture for the user and control planes in LTE. The radio protocol architecture for the UE and the eNodeB is shown with three layers:Layer 1,Layer 2, andLayer 3. Layer 1 (L1 layer) is the lowest layer and implements various physical layer signal processing functions. The L1 layer will be referred to herein as thephysical layer506. Layer 2 (L2 layer)508 is above thephysical layer506 and is responsible for the link between the UE and eNodeB over thephysical layer506.
• In the user plane, theL2 layer508 includes a media access control (MAC)sublayer510, a radio link control (RLC)sublayer512, and a packet data convergence protocol (PDCP)514 sublayer, which are terminated at the eNodeB on the network side. Although not shown, the UE may have several upper layers above theL2 layer508 including a network layer (e.g., IP layer) that is terminated at thePDN gateway118 on the network side, and an application layer that is terminated at the other end of the connection (e.g., far end UE, server, etc.).
• ThePDCP sublayer514 provides multiplexing between different radio bearers and logical channels. ThePDCP sublayer514 also provides header compression for upper layer data packets to reduce radio transmission overhead, security by ciphering the data packets, and handover support for UEs between eNodeBs. TheRLC sublayer512 provides segmentation and reassembly of upper layer data packets, retransmission of lost data packets, and reordering of data packets to compensate for out-of-order reception due to hybrid automatic repeat request (HARQ). TheMAC sublayer510 provides multiplexing between logical and transport channels. TheMAC sublayer510 is also responsible for allocating the various radio resources (e.g., resource blocks) in one cell among the UEs. TheMAC sublayer510 is also responsible for HARQ operations.
• In the control plane, the radio protocol architecture for the UE and eNodeB is substantially the same for thephysical layer506 and theL2 layer508 with the exception that there is no header compression function for the control plane. The control plane also includes a radio resource control (RRC)sublayer516 in Layer 3 (L3 layer). TheRRC sublayer516 is responsible for obtaining radio resources (i.e., radio bearers) and for configuring the lower layers using RRC signaling between the eNodeB and the UE.
• FIG. 6 is a block diagram of aneNodeB610 in communication with aUE650 in an access network. In the downlink, upper layer packets from the core network are provided to a controller/processor675. The controller/processor675 implements the functionality of the L2 layer. In the downlink, the controller/processor675 provides header compression, ciphering, packet segmentation and reordering, multiplexing between logical and transport channels, and radio resource allocations to theUE650 based on various priority metrics. The controller/processor675 is also responsible for HARQ operations, retransmission of lost packets, and signaling to theUE650.
• TheTX processor616 implements various signal processing functions for the L1 layer (i.e., physical layer). The signal processing functions includes coding and interleaving to facilitate forward error correction (FEC) at theUE650 and mapping to signal constellations based on various modulation schemes (e.g., binary phase-shift keying (BPSK), quadrature phase-shift keying (QPSK), M-phase-shift keying (M-PSK), M-quadrature amplitude modulation (M-QAM)). The coded and modulated symbols are then split into parallel streams. Each stream is then mapped to an OFDM subcarrier, multiplexed with a reference signal (e.g., pilot) in the time and/or frequency domain, and then combined together using an Inverse Fast Fourier Transform (IFFT) to produce a physical channel carrying a time domain OFDM symbol stream. The OFDM stream is spatially precoded to produce multiple spatial streams. Channel estimates from achannel estimator674 may be used to determine the coding and modulation scheme, as well as for spatial processing. The channel estimate may be derived from a reference signal and/or channel condition feedback transmitted by theUE650. Each spatial stream is then provided to adifferent antenna620 via a separate transmitter618TX. Each transmitter618TX modulates an RF carrier with a respective spatial stream for transmission.
• At theUE650, each receiver654RX receives a signal through itsrespective antenna652. Each receiver654RX recovers information modulated onto an RF carrier and provides the information to the receiver (RX)processor656. TheRX processor656 implements various signal processing functions of the L1 layer. TheRX processor656 performs spatial processing on the information to recover any spatial streams destined for theUE650. If multiple spatial streams are destined for theUE650, they may be combined by theRX processor656 into a single OFDM symbol stream. TheRX processor656 then converts the OFDM symbol stream from the time-domain to the frequency domain using a Fast Fourier Transform (FFT). The frequency domain signal comprises a separate OFDM symbol stream for each subcarrier of the OFDM signal. The symbols on each subcarrier, and the reference signal, is recovered and demodulated by determining the most likely signal constellation points transmitted by theeNodeB610. These soft decisions may be based on channel estimates computed by thechannel estimator658. The soft decisions are then decoded and deinterleaved to recover the data and control signals that were originally transmitted by theeNodeB610 on the physical channel. The data and control signals are then provided to the controller/processor659.
• The controller/processor659 implements the L2 layer. The controller/processor can be associated with amemory660 that stores program codes and data. Thememory660 may be referred to as a computer-readable medium. In the uplink, the controller/processor659 provides demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, control signal processing to recover upper layer packets from the core network. The upper layer packets are then provided to adata sink662, which represents all the protocol layers above the L2 layer. Various control signals may also be provided to the data sink662 for L3 processing. The controller/processor659 is also responsible for error detection using an acknowledgement (ACK) and/or negative acknowledgement (NACK) protocol to support HARQ operations.
• In the uplink, adata source667 is used to provide upper layer packets to the controller/processor659. Thedata source667 represents all protocol layers above the L2 layer. Similar to the functionality described in connection with the downlink transmission by theeNodeB610, the controller/processor659 implements the L2 layer for the user plane and the control plane by providing header compression, ciphering, packet segmentation and reordering, and multiplexing between logical and transport channels based on radio resource allocations by theeNodeB610. The controller/processor659 is also responsible for HARQ operations, retransmission of lost packets, and signaling to theeNodeB610.
• Channel estimates derived by achannel estimator658 from a reference signal or feedback transmitted by theeNodeB610 may be used by theTX processor668 to select the appropriate coding and modulation schemes, and to facilitate spatial processing. The spatial streams generated by theTX processor668 are provided todifferent antenna652 via separate transmitters654TX. Each transmitter654TX modulates an RF carrier with a respective spatial stream for transmission.
• The uplink transmission is processed at theeNodeB610 in a manner similar to that described in connection with the receiver function at theUE650. Each receiver618RX receives a signal through itsrespective antenna620. Each receiver618RX recovers information modulated onto an RF carrier and provides the information to aRX processor670. TheRX processor670 may implement the L1 layer.
• The controller/processor675 implements the L2 layer. The controller/processor675 can be associated with amemory676 that stores program codes and data. Thememory676 may be referred to as a computer-readable medium. In the uplink, the controller/processor675 provides demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, control signal processing to recover upper layer packets from theUE650. Upper layer packets from the controller/processor675 may be provided to the core network. The controller/processor675 is also responsible for error detection using an ACK and/or NACK protocol to support HARQ operations.
Determining MPR for Wireless Communication Systems
• Wireless communication standards, such as the 3GPP standard, define a maximum power reduction (MPR) value for a user equipment (UE) to lower its maximum output power to meet a specified signal quality value and/or out of band (OOB) emissions value. In a typical system, the maximum power reduction value is a function of the modulation scheme, the channel bandwidth, and the transmission bandwidth (e.g., the number of transmitted resource blocks).
• In some cases, the 3GPP standard specifies wireless transmissions via noncontiguous clusters. The transmission of noncontiguous clusters in some networks, such as LTE networks, may produce interference in adjacent frequency channels because of increased out of band emissions. In some cases, the increased out band emissions are caused by intermodulation distortion due to non-linearity of the transmitter power amplifier. In some networks, such as LTE networks, out of band emissions are defined using a first spectrum emission mask (SEM), a second spectrum emission mask, and an adjacent channel leakage ratio.
• Spurious emissions occur outside of the bandwidth used for transmission and are caused by a variety of non-ideal effects, such as, for example, harmonic emissions and/or intermodulation products. Both out of band emissions and spurious emissions due to intermodulation distortion are generated at specific frequencies. The specific frequencies depend on the cluster separation. As the frequency separation between clusters increases, the intermodulation distortion spread increases and the specified maximum power reduction increases (e.g., becomes more stringent).
• A typical amplifier is a non-linear device that may produce undesirable intermodulation products. The intermodulation products may include the sum and difference of the cluster frequencies F1 and F2 at multiples of the sum and difference frequencies, such as 2F1−F2 or 3F1−2F2. In some cases, the order of the intermodulation products may be calculated by adding the constants used to multiply cluster frequencies F1 and F2 in the intermodulation product. In one configuration, (2F1−F2) is a third order intermodulation product and (3F1−2F) is a fifth order intermodulation product.
• Wireless communication standards, such as the 3GPP standard, determine the maximum power reduction values based on a total number of active resource blocks for multi-cluster waveforms. In some cases, when the number of active resource blocks is reduced, the maximum power reduction value is increased. In a typical network, the maximum power reduction may degrade network performance due to increased power reduction by UEs.
• Aspects of the present disclosure define a maximum power reduction based on a number of resource blocks to be transmitted and additional criteria. In one configuration, the maximum power reduction is determined using formulas for estimating locations of the third and fifth order products created by multi-clusters. The formula accounts for gap information, edge information, and balance information for each of the resource blocks of the clusters. Based on aspects of the present disclosure, unnecessary power reductions by the UE are mitigated and UE throughput and network capacity are improved.
• FIG. 7 shows aspectrum700 of two clusters F1, F2.FIG. 7 further illustrates the third orderintermodulation distortion products702 and the fifth orderintermodulation distortion products704 associated with the two clusters F1, F2. The position of the third orderintermodulation distortion products702 and fifth orderintermodulation distortion products704 are shown as a function of the center frequencies of the two clusters F1, F2. For example, the center frequencies of third orderintermodulation distortion products702 are generally 2F1−F2 and 2F2−F1. The center frequencies of the fifth orderintermodulation distortion products704 are generally 3F1−2F2 and 3F2−2F1.
• Aspects of the present disclosure provide improved predictions of the locations of the third order and fifth order intermodulation distortion products including predictions of their gaps and bandwidth.FIG. 8 shows positions of twoclusters800,800′.FIG. 8 further illustrates the associated third orderintermodulation distortion products802,802′ and the fifth orderintermodulation distortion products804,804′. In one configuration, the positions of the third orderintermodulation distortion products802,802′ and the fifth orderintermodulation distortion products804,804′ are determined based on bandwidth boundaries of the associatedclusters800,800′. In one configuration, the lower boundary of the first (lower frequency)cluster800 is represented by the first cluster start index (F1_ST) and the upper boundary of thefirst cluster800 is represented by the first cluster stop index (F1_SP). Additionally, in the present configuration, the lower boundary of the second (upper frequency)cluster800′ is represented by the second cluster start index (F2_ST) and the upper boundary of thesecond cluster800′ is represented by the second cluster stop index (F2_SP).
• According to an aspect of the present disclosure, the lower boundary of the lower third orderintermodulation distortion product802 is represented by the index (3L_ST) and the upper boundary of the lower third orderintermodulation distortion product802 is represented by the index (3L_SP). Additionally, in the present configuration, the lower boundary of the lower fifth orderintermodulation distortion product804 is represented by the index (5L_ST) and the upper boundary of the lower fifth orderintermodulation distortion product804 is represented by the index (5L_SP). Moreover, in the present configuration, the lower boundary of the upper third orderintermodulation distortion product802′ is represented by the index (3H_ST) and the upper boundary of the upper third orderintermodulation distortion product802′ is represented by the index (3H_SP). Furthermore, in the present configuration, the lower boundary of the upper fifth orderintermodulation distortion product804′ is represented by the index (5H_ST) and the upper boundary of the upper fifth orderintermodulation distortion product804′ is represented by the index (5H_SP). Finally, in the present configuration, the frequency offset values defining boundary positions of the third order intermodulation and the fifth order intermodulation distortion products are predicted by the following equations:
• 
  3L_—ST=2×F1_—ST−F2_—SP  (1)
• 
  3L_—SP=2(F1_—SP+1)−F2_—ST  (2)
• 
  5L_—ST=2×3L_—ST−F1_—SP  (3)
• 
  5L_—SP=2×3L_—SP−F1_—ST  (4)
• 
  3H_—ST=2×F2_—SP−F1_—ST  (5)
• 
  3H_—SP=2×F2_—ST−(F1_—SP+1)   (6)
• 
  5H_—SP=2×3H_—SP−F2_—ST  (7)
• 
  5L_—SP=2×3H_—ST−F2_—SP  (8)
• According to an aspect of the present disclosure, after calculating the frequency offset values that define spectral positions of the third and fifth order intermodulation distortion products using EQUATIONS 1-8, the spectral positions are mapped to a spectral region index using the calculated frequency offset. The spectral region index boundaries may vary depending on the number of resource blocks being transmitted.FIG. 9 illustrates a frequency mapping to a resource block (RB) index for a spectrum emission mask, according to an aspect of the present disclosure.
• In one configuration, as shown inFIG. 9, the region index values may be based on frequency offsets in aspectrum emission mask902. In this configuration, five regions (1-5) are defined on each side of achannel904. Thechannel904 may be a 20 MHz channel. As shown inFIG. 9, thechannel904 is region zero. Based on the RB Index, the RB index for thechannel904 begins from 1 RB and may increase to 100 RB depending on the channel bandwidth. In one configuration, based on a frequency and assuming a channel bandwidth for thechannel904 is 20 MHz (−10 MHZ to 10 MHz), the first RB begins at 9 MHz below the center frequency, fc −9 MHz, and last RB index, 100, is 9 MHz above the center frequency, fc +9 MHz.
• In yet another configuration, non-linearity of the power amplifier may be determined, for example during calibration. The amount of non-linearity could then be factored into the MPR determination.
• According to one aspect of the present disclosure, a region index value for each of the intermodulation distortion products is determined based on calculation of the outer spectral boundaries of third order products (3L_ST and 3H_SP) and the outer spectral boundaries of the fifth order products (5L_ST and 5H_SP). For example, as shown inFIG. 9, if the calculated frequency offset of the outer boundary of the lower third order intermodulation product (3L_ST) is between −15 MHz and −11 MHz, then the region index of the lower third order intermodulation distortion product is two. Stated another way, based on the RB index, if lower third order intermodulation product (3L_ST) is between −33 to −10 RBs, then the region index is two.
• Although the present configuration is described with reference to the outside boundaries of respective intermodulation products, aspects of the present disclosure are also contemplated for assigning region boundaries based on center frequencies or inner boundaries of the intermodulation distortion products. The boundaries of each region may vary depending on the number of transmitted resource blocks, for example. In one configuration, the boundaries of the regions are fixed, in terms of RBs. Still, the signal is defined by the variables F1_ST and F1_SP or F2_ST and F2_SP. The bandwidth for each of these signals is embedded into the values assigned to the variables. The variables are used in EQUATIONS 1-8 which define the third and fifth order lower and upper frequencies. The third and fifth order lower and upper frequencies are then compared to the fixed regions.
• FIG. 10 shows an exemplary region index combination and maximum specified backoff. Referring to table1000, according to an aspect of the present disclosure, a particularmaximum power reduction1002 is listed (in dB) for each combination in a list of different region index combinations. The first column1004 represents the region index corresponding to the lower fifth order intermodulation product, the second column1006 represents the region index corresponding to the lower third order intermodulation distortion product, the third column1008 represents the region index corresponding to the upper third order intermodulation distortion product, and the fourth column1010 represents the region index corresponding to the upper fifth order intermodulation distortion product. For example, a waveform having intermodulation distortion products with a region index combination of 3-0-3-3 would be assigned a power back off of 2.57 dB.
• The power backoff for waveforms transmitted by a UE, which have the same region indices, may not be the same. For example, an error between the maximum power reduction and specified backoff may be between 2 dB and 5 dB depending on resource block ratio, distance from edge, and/or separation between clusters. To reduce the aforementioned errors, additional rules (i.e., mappings) may be specified to define the maximum power reduction for two-cluster transmissions having an unbalanced resource block ratio between clusters.
• The additional rules (i.e., a mapping different fromFIG. 10) may be applied forunbalanced clusters1102,1104, as shown inFIG. 11. For two clusters carrying a combined total of twenty resource blocks, the additional rules may be applied when the resource block ratio is between 1:19 and 4:16. That is, the additional rules forunbalanced clusters1102,1104 may be applied if one of theunbalanced clusters1102 has less than five resource blocks out of the twenty total resource blocks of both clusters. In one configuration, the rule may only be applied to clusters with twenty or more resource blocks because the improvements to the system may not be achieved for clusters with less than twenty resource blocks. Of course, the aspects of the present disclosure are not limited to clusters with twenty or more resource blocks.
• A method of defining the applied maximum power reduction depending on the total number of resource blocks (RBs) for balanced and unbalanced clusters according to an aspect of the present disclosure is described with reference toFIG. 12. Inblock1202, an eNodeB schedules a multi-cluster uplink transmission for a UE. In one configuration, the multi-cluster uplink transmission is a two-cluster uplink transmission, the modulation and coding scheme (MCS) is QPSK, and the total bandwidth is 20 MHz. Inblock1204, the UE calculates the position of the third and fifth order intermodulation distortion products for the resource blocks to be transmitted. Furthermore, inblock1206, the UE determines whether the total number of resource blocks is less than twenty. If the total number of resource blocks is less than twenty, the UE defines region indices based on the calculated positions of the third and fifth intermodulation distortion products inblock1208 and defines the maximum power reduction based on the region indices inblock1210.
• In one configuration, when the total number of resource blocks is equal to or greater than twenty, then the UE determines whether one of the two clusters has less than four resource blocks inblock1212. If neither of the two clusters has less than four resource blocks, the UE defines the region indices based on the calculated positions of the third and fifth intermodulation distortion products inblock1214 and defines the maximum power reduction based on the region indices inblock1216. If one of the two clusters has less than four resource blocks, the UE determines the region indices based on the aforementioned rules for unbalanced clusters inblock1218 and defines the maximum power reduction based on the region indices inblock1220.
• FIG. 13 illustrates amethod1300 of wireless communication according to aspects of the present disclosure. Inblock1302, a UE determines spectral positions of third and fifth order intermodulation distortion products for a multi-cluster transmission. The determined positions may also include the gaps and bandwidth for the intermodulation distortion products. Inblock1304, the UE maps the spectral positions of frequencies and resource blocks to corresponding spectral regions. The UE may also map the spectral positions of the gaps and bandwidth for the intermodulation distortion products. Inblock1306, the UE determines a maximum power reduction value of the multi-cluster transmission based on the corresponding spectral regions.
• FIG. 14 illustrates amethod1400 of wireless communication according to aspects of the present disclosure. Inblock1402, a UE determines determine spectral positions of third and fifth order intermodulation distortion products for a multi-cluster transmission including positions of the gaps and bandwidth of the intermodulation distortion products. The UE may also determine the positions of the gaps and bandwidth for the multi-cluster transmission. Inblock1404, the UE maps the spectral frequencies and resource block positions to corresponding spectral regions. Inblock1406, the UE determine a maximum power reduction value of the multi-cluster transmission based on the corresponding spectral regions, gap information, edge information, balance information, and/or number of resource blocks to be transmitted.
• FIG. 15 is a diagram illustrating an example of a hardware implementation for anapparatus1500 employing apower control system1515 according to one aspect of the disclosure. Thepower control system1515 may be implemented with a bus architecture, represented generally by abus1524. Thebus1524 may include any number of interconnecting buses and bridges depending on the specific application of thepower control system1515 and the overall design constraints. Thebus1524 links together various circuits including one or more processors and/or hardware modules, represented by aprocessor1526, a first determiningmodule1502, amapping module1504, a second determiningmodule1506, and a computer-readable medium1528. Thebus1524 may also link various other circuits such as timing sources, peripherals, voltage regulators, and power management circuits, which are well known in the art, and therefore, will not be described any further.
• Theapparatus1500 includes thepower control system1515 coupled to atransceiver1522. Thetransceiver1522 is coupled to one ormore antennas1520. Thetransceiver1522 communicates with various other apparatus over a transmission medium. Thepower control system1515 includes theprocessor1526 coupled to the computer-readable medium1528. Theprocessor1526 is responsible for general processing, including the execution of software stored on the computer-readable medium1528. The software, when executed by theprocessor1526, causes thepower control system1515 to perform the various functions described supra for any particular apparatus. The computer-readable medium1528 may also be used for storing data that is manipulated by theprocessor1526 when executing software.
• Thepower control system1515 further includes a first determiningmodule1502 that determines spectral positions of intermodulation distortion products for a multi-cluster transmission. The first determiningmodule1502 receives the intermodulation distortion products from theprocessor1526. Thepower control system1515 also includes amapping module1504 that maps the spectral positions corresponding to the spectral regions. Themapping module1504 forwards the spectral positions to a second determiningmodule1506. The second determiningmodule1506 determines a maximum power reduction value of the multi-cluster transmission based on the corresponding spectral region. In one configuration, the first determiningmodule1502 and the second determiningmodule1506 may be a single module (not shown). Additionally, the first determiningmodule1502, themapping module1504 and the second determiningmodule1506 may be software modules running in theprocessor1526, resident/stored in the computer-readable medium1528, one or more hardware modules coupled to theprocessor1526, or some combination thereof. Thepower control system1515 may be a component of theUE650 and may include thememory660 and/or the controller/processor659, for example, as shown inFIG. 6.
• In one configuration, theapparatus1500 for wireless communication includes means for determining. The determining means may include the first determiningmodule1502, the second determiningmodule1506, thepower control system1515, the controller/processor659, and/or thememory660 configured to perform the functions recited by the determining means. In another configuration, the determining means may be any module or any apparatus configured to perform the functions recited by the determining means.
• In one configuration, theapparatus1500 for wireless communication includes means for mapping. The mapping means may include themapping module1504, thepower control system1515, the controller/processor659, and/or thememory660 configured to perform the functions recited by the mapping means. In another configuration, the mapping means may be any module or any apparatus configured to perform the functions recited by the mapping means.
• The examples above describe aspects implemented in an LTE/-A system. However, the scope of the disclosure is not so limited. Various aspects may be adapted for use with other communication systems, such as those that employ any of a variety of communication protocols including, but not limited to, CDMA systems, TDMA systems, FDMA systems, and OFDMA systems.
• Those of skill would further appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the disclosure herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present disclosure.
• The various illustrative logical blocks, modules, and circuits described in connection with the disclosure herein may be implemented or performed with a general-purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.
• The steps of a method or algorithm described in connection with the disclosure herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. The processor and the storage medium may reside in an ASIC. The ASIC may reside in a user terminal. In the alternative, the processor and the storage medium may reside as discrete components in a user terminal.
• In one or more exemplary designs, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Computer-readable media includes both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. A storage media may be any available media that can be accessed by a general purpose or special purpose computer. By way of example, and not limitation, such computer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code means in the form of instructions or data structures and that can be accessed by a general-purpose or special-purpose computer, or a general-purpose or special-purpose processor. Also, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. Disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.
• The previous description of the disclosure is provided to enable any person skilled in the art to make or use the disclosure. Various modifications to the disclosure will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other variations without departing from the spirit or scope of the disclosure. Thus, the disclosure is not intended to be limited to the examples and designs described herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (20)

What is claimed is:

1. A method of wireless communication, comprising:

determining spectral positions of intermodulation distortion products for a multi-cluster transmission;

mapping the spectral positions to corresponding spectral regions; and

determining a maximum power reduction value of the multi-cluster transmission based at least in part on the corresponding spectral regions.

2. The method ofclaim 1, in which the mapping further comprises mapping the spectral positions of at least one gap and a bandwidth of each intermodulation distortion product.

3. The method ofclaim 1, further comprising:

determining boundaries of the spectral positions, and

in which the mapping is based at least in part on the boundaries of the spectral positions.

4. The method ofclaim 3, in which the mapping further comprises mapping frequencies and resource blocks.

5. The method ofclaim 1, further comprising:

determining a combination of the spectral regions corresponding to at least one of a third order intermodulation distortion product, or a fifth order intermodulation distortion product, for the multi-cluster transmission; and

determining the maximum power reduction value based on the combination.

6. The method ofclaim 1, further comprising;

determining whether the multi-cluster transmission includes a balanced number of resource blocks based on a predetermined resource block ratio threshold;

determining the maximum power reduction value using a first mapping of region indices when the multi-cluster transmission includes the balanced number of resource blocks; and

determining the maximum power reduction values using a second mapping of region indices when the multi-cluster transmission includes an unbalanced number of resource blocks.

7. The method ofclaim 1, further comprising defining the spectral regions based at least in part on a number of resource blocks associated with the multi-cluster transmission.

8. An apparatus for wireless communication, comprising:

a memory; and

at least one processor coupled to the memory, the at least one processor being configured:

to determine spectral positions of intermodulation distortion products for a multi-cluster transmission;

to map the spectral positions to corresponding spectral regions; and

to determine a maximum power reduction value of the multi-cluster transmission based at least in part on the corresponding spectral regions.

9. The apparatus ofclaim 8, in which the at least one processor is further configured to map the spectral positions of at least one gap and a bandwidth of each intermodulation distortion product.

10. The apparatus ofclaim 8, in which the at least one processor is further configured:

to determine boundaries of the spectral positions; and

to map the spectral positions to the corresponding spectral regions based at least in part on the boundaries of the spectral positions.

11. The apparatus ofclaim 10, in which the at least one processor is further configured to map frequencies and resource blocks.

12. The apparatus ofclaim 8, in which the at least one processor is further configured:

to determine a combination of the spectral regions corresponding to at least one of a third order intermodulation distortion product, or a fifth order intermodulation distortion product, for the multi-cluster transmission; and

to determine the maximum power reduction value based on the combination.

13. The apparatus ofclaim 8, in which the at least one processor is further configured:

to determine whether the multi-cluster transmission includes a balanced number of resource blocks based on a predetermined resource block ratio threshold;

to determine the maximum power reduction value using a first mapping of region indices when the multi-cluster transmission includes the balanced number of resource blocks; and

to determine the maximum power reduction values using a second mapping of region indices when the multi-cluster transmission includes an unbalanced number of resource blocks.

14. The apparatus ofclaim 8, in which the at least one processor defines the spectral regions based at least in part on a number of resource blocks associated with the multi-cluster transmission.

15. An apparatus operable for wireless communication, comprising:

means for determining spectral positions of intermodulation distortion products for a multi-cluster transmission;

means for mapping the spectral positions to corresponding spectral regions; and

means for determining a maximum power reduction value of the multi-cluster transmission based at least in part on the corresponding spectral regions.

16. The apparatus ofclaim 15, further comprising:

means for determining boundaries of the spectral positions; and

means for mapping the spectral positions to the corresponding spectral regions based at least in part on the boundaries of the spectral positions.

17. The apparatus ofclaim 15, further comprising:

means for determining a combination of the spectral regions corresponding to at least one of a third order intermodulation distortion product or a fifth order intermodulation distortion product, for the multi-cluster transmission; and

means for determining the maximum power reduction value based on the combination.

18. A computer program product operable for wireless communication, the computer program product comprising:

a non-transitory computer-readable medium having program code recorded thereon, the program code comprising:

program code to determine spectral positions of intermodulation distortion products for a multi-cluster transmission;

program code to map the spectral positions to corresponding spectral regions; and

program code to determine a maximum power reduction value of the multi-cluster transmission based at least in part on the corresponding spectral regions.

19. The computer program product ofclaim 18, in which the program code further comprises:

program code to determine boundaries of the spectral positions; and

program code to map the spectral positions to the corresponding spectral regions based at least in part on the boundaries of the spectral positions.

20. The computer program product ofclaim 18, in which the program code further comprises:

program code to determine a combination of the spectral regions corresponding to at least one of a third order intermodulation distortion product or a fifth order intermodulation distortion product, for the multi-cluster transmission; and

program code to determine the maximum power reduction value based on the combination.

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